1. Technical Field
Example embodiments of the present invention generally relate to a sheet alignment device, and/or a sheet processing apparatus including the sheet alignment device, and/or an image processing system including an image forming apparatus connected to or integrally mounted with the sheet processing apparatus including the sheet alignment device. More particularly, the present invention relates to a sheet alignment device that aligns sheet-type recording media, and/or a sheet finishing apparatus that includes such a sheet alignment device and executes operations such as sorting, stacking, binding or stapling, folding, punching, and the like with respect to the recording media, and/or an image processing system including an image forming apparatus integrally mounted with or connected to the sheet finishing apparatus including the sheet alignment device.
2. Discussion of the Related Art
Sheet processing is executed for aligning paper sheets in both a sheet travel direction and a direction perpendicular to the sheet travel direction. When aligning paper sheets in the direction perpendicular to the sheet travel direction, which is hereinafter referred to as a “sheet width direction”, a pair of alignment members is used. One of such pairs of alignment members is generally called as “jogger fences.”
In one technique of sheet alignment, a related art sheet finishing apparatus includes a processing tray to temporarily stack discharged paper sheets to reduce a moment load applied to alignment members, a pair of discharging rollers to discharge the paper sheets onto the processing tray, and a pair of alignment members disposed at both sides of paper sheet in the sheet width direction to align the paper sheets on the processing tray along the sheet width direction. At least one of the pair of alignment members is flexibly movable in the sheet width direction. With the above-described structure, the pair of alignment members of the related art sheet finishing apparatus form respective protruding portions on alignment surfaces of the pair of alignment members facing each other so as to overlap in a position of a sheet discharging direction.
In a different technique of sheet alignment, to neatly align paper sheet regardless of a reference position during sheet conveyance, sheet size, and the like, a tamper is movably arranged to face a lateral reference wall is provided with a lever. With the lever on the tamper, paper sheets can be aligned while lifting the end part at the tamper side of a newly supplied paper sheet. Accordingly, the end part of the newly supplied paper sheet is caught between the paper sheet that is already aligned and the tamper, and is folded to cause a situation of sheet alignment error.
In a further different technique of sheet alignment, a related art sheet finishing apparatus includes a sheet handling device that can prevent the overlap of the bound positions of stapled sheet stacks on a sheet discharging tray. Specifically, the conveyed sheets are placed on a stacking tray and adjusted by an adjusting plate and a shutter. After binding a sheet stack by a stapler, the sheet stack is discharged and placed on the sheet discharging tray by a pair of discharging rollers. Each bound position of each sheet stack on the sheet discharging tray is displaced by a displacing unit so as not to overlap each other. Accordingly, the related art sheet finishing apparatus can prevent a sheet stacking failure caused by the overlap of the binding positions.
When binding or stapling the end portions of a sheet stack, related art sheet finishing apparatuses generally execute a sheet alignment in a sheet width direction with a pair of alignment members operating at the same time. With such a structure, however, both side ends of sheet stack cannot be properly aligned. Specifically, since sheet stack has variations of distance in the sheet width direction, when the pair of alignment members pushes both end sides of the sheet stack, the sheet stack may be tossed to undetermined side and may keep non-uniform surface of the end sides thereof.
To eliminate the drawback, the above-described technique in which one of the pair of alignment members moves to align sheet stack and the other one of the pair of alignment members is fixed at a given position on one side of the tray to stop the sheet stack pushed by the opposite alignment member. With the above-described structure, however, the side end of the sheet stack that is pushed to the stopping alignment member may not sufficiently be aligned. In addition, when one of the pair of alignment members is completely fixed at and cannot move from a sheet receiving position, the other alignment member, which is a movable alignment member, may need to move by a greater of distance along the sheet width direction, which can result in a requirement of a longer operation period.